1. Field Of The Invention
The invention relates to a process for the preparation of arylamides of heteroaromatic carboxylic acids by reacting heteroaromatic halogen compounds with carbon monoxide and aromatic amines in the presence of a catalyst and a base. The invention further relates to a novel halogenopyridine as a starting material for the preparation, according to the invention, of an arylamide.
The amides which can be prepared according to the invention have the general formula: ##STR2## in which: A.sup.1 is nitrogen or CR.sup.1,
A.sup.2 is nitrogen or CR.sup.2,
A.sup.3 is nitrogen or CR.sup.3,
A.sup.4 is nitrogen or CR.sup.4 and
A.sup.5 is nitrogen or CR.sup.5,
with the proviso that at least one of the ring members A.sup.1 to A.sup.5 is nitrogen and that two nitrogen atoms are not bonded directly to one another;
R.sup.1 to R.sup.5, if present, independently of one another are hydrogen, C.sub.1-4 -alkyl or aryl, but one of the substituents R.sup.1 to R.sup.5 is a group of the formula --OR, in which R is an optionally substituted aromatic or heteroaromatic radical;
R.sup.6 is hydrogen or C.sub.1-4 -alkyl; and
R.sup.7 is an optionally substituted aromatic or heteroaromatic radical.
Said amides include especially the arylamides of pyridine-, pyrimidine-, pyrazine- and 1,3,5-triazinecarboxylic acids.
2. Background Art
Numerous compounds of the structure of formula I, especially those in which one of the substituents R.sup.1 to R.sup.5 is an aryloxy group (--OR) adjacent to a ring nitrogen atom, are important herbicides (International Published Patent Application No. 94/27974, European Published Patent Application No. 0,053,011 and European Published Patent Application No. 0,447,004). The synthesis of these known compounds is conventionally based on the corresponding carboxylic acids or carboxylic acid derivatives (acid chlorides, esters, nitriles), although these are often difficult to obtain and therefore expensive.